Teradata Database supports two session modes:
ANSI
Teradata
In ANSI session mode:
Transaction processing follows the rules defined by the ANSI/ISO SQL:2011 standard.
For Teradata SQL features that support both the ANSI/ISO SQL standard syntax and the
Teradata SQL dialect, the ANSI/ISO SQL standard syntax is used.
The default case specification for character data is CASESPECIFIC.
When a character string requires truncation, the excess pad characters are truncated
without reporting an error. Truncation of characters other than trailing nonblank
characters results in a truncation exception.
Cursors are always positioned. Updating or deleting the most current fetched cursor
row using the UPDATE/DELETE … WHERE CURRENT OF statement is valid.
The default table type is MULTISET, which allows duplicate rows.
The TRIM function trims both leading and trailing pad characters by default.
In Teradata session mode:
Transaction processing follows the rules defined by Teradata before the emergence
of the ANSI/ISO SQL standard. These rules largely conform with ANSI/ISO semantics,
but in some cases differ in important ways from the ANSI/ISO semantics.
For Teradata SQL features that support both the ANSI/ISO SQL standard syntax and the
Teradata SQL dialect, the Teradata SQL syntax is used.
By default, character data is NOT CASESPECIFIC, except when the character set is GRAPHIC.
GRAPHIC character data by default is CASESPECIFIC.
The default case specification for character data is NOT CASESPECIFIC. The exception
is data of type CHARACTER (n) CHARACTER SET GRAPHIC, which is always CASESPECIFIC.
When a character string requires truncation, the string is truncated silently with
no truncation notification given. This is true for truncation of pad or non-pad characters.
Cursors are never positioned. Updating or deleting the most current fetched cursor
row using the UPDATE/DELETE … WHERE CURRENT OF statement is not valid.
The default table type depends on whether the table has a primary index. Tables with
a PI are SET (do not allow duplicate rows). Tables without a primary index (including
column-partitioned tables) are MULTISET (allow duplicate rows).
The TRIM function trims only trailing pad characters by default.
Note: Case specificity does not apply to CLOBs.
A transaction is a logical unit of work. The statements nested within the transaction
either execute successfully as a group or do not execute. A Teradata SQL transaction
can be a single Teradata SQL statement, or a sequence of Teradata SQL statements.